title: Substrate specificity and oligomerization of human GMP synthetase.
abstract: Guanine monophosphate (GMP) synthetase is a bifunctional two-domain enzyme. The N-terminal glutaminase domain generates ammonia from glutamine and the C-terminal synthetase domain aminates xanthine monophosphate (XMP) to form GMP. Mammalian GMP synthetases (GMPSs) contain a 130-residue-long insert in the synthetase domain in comparison to bacterial proteins. We report here the structure of a eukaryotic GMPS. Substrate XMP was bound in the crystal structure of the human GMPS enzyme. XMP is bound to the synthetase domain and covered by a LID motif. The enzyme forms a dimer in the crystal structure with subunit orientations entirely different from the bacterial counterparts. The inserted sub-domain is shown to be involved in substrate binding and dimerization. Furthermore, the structural basis for XMP recognition is revealed as well as a potential allosteric site. Enzymes in the nucleotide metabolism typically display an increased activity in proliferating cells due to the increased need for nucleotides. Many drugs used as immunosuppressants and for treatment of cancer and viral diseases are indeed nucleobase- and nucleoside-based compounds, which are acting on or are activated by enzymes in this pathway. The information obtained from the crystal structure of human GMPS might therefore aid in understanding interactions of nucleoside-based drugs with GMPS and in structure-based design of GMPS-specific inhibitors.
authors.affiliation: Structural Genomics Consortium, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, S-17177 Stockholm, Sweden.
authors.forename: Martin
authors.initials: M
authors.lastname: Welin
authors.forename: Lari
authors.initials: L
authors.lastname: Lehtiö
authors.forename: Andreas
authors.initials: A
authors.lastname: Johansson
authors.forename: Susanne
authors.initials: S
authors.lastname: Flodin
authors.forename: Tomas
authors.initials: T
authors.lastname: Nyman
authors.forename: Lionel
authors.initials: L
authors.lastname: Trésaugues
authors.forename: Martin
authors.initials: M
authors.lastname: Hammarström
authors.forename: Susanne
authors.initials: S
authors.lastname: Gräslund
authors.forename: Pär
authors.initials: P
authors.lastname: Nordlund
mesh_terms: D000595:Amino Acid Sequence; D019731:Carbon-Nitrogen Ligases / Q000737:chemistry* / Q000378:metabolism*; D004926:Escherichia coli / Q000737:chemistry / Q000201:enzymology; D006801:Humans; D007700:Kinetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011485:Protein Binding; D011487:Protein Conformation; D054730:Protein Interaction Domains and Motifs; D055503:Protein Multimerization; D016415:Sequence Alignment; D013379:Substrate Specificity
chemical_list: D019731:Carbon-Nitrogen Ligases; C020828:GMP synthase (glutamine-hydrolyzing)
keywords: 6-diazo-5-oxo-l-norleucine; ATP pyrophosphatase; ATPPase; DON; EcGMPS; Escherichia coli GMPS; GATase; GMP; GMP synthetase; GMPS; PDB; PhGMPS; Protein Data Bank; Pyrococcus horikoshii OT3 GMPS; Thermus thermophilus GMPS; TtGMPS; XMP; amidotransferase; crystal structure; glutaminase; guanine monophosphate; hGMPS; human GMPS; oligomerization; substrate specificity; xanthine monophosphate